ML20206H113

Submits DHEAT2 Parametric Calculations for Plant,Per 860620 Discussions.Calculations Run Assuming Any Steam Spike Would Develop Too Slowly to Contribute to DCH Peak Pressure

ML20206H113
Person / Time
Site:	Surry, 05000000
Issue date:	06/23/1986
From:	David Williams SANDIA NATIONAL LABORATORIES
To:	Lee T NRC OFFICE OF NUCLEAR REGULATORY RESEARCH (RES)
Shared Package
ML20204G644	List: ML20206C066 ML20206E142 ML20206F071 ML20206F086 ML20206F182 ML20206F313 ML20206G821 ML20206G928 ML20206H081 ML20206H113 ML20206H144 ML20206J252 ML20206J270 ML20206J368 ML20206J403 ML20206J600
References
RTR-NUREG-1150 NUDOCS 8704150260
Download: ML20206H113 (2)

Text

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., d f.17 Sandia National Laboratories Albuquerque, New Mexico 87185 June 23, 1986 Dr. Tim M. Lee NRC/RES 7915 Eastern Avenue Silver Spring, MD 20910

Dear Dr. Lee:

As per our discussions last Friday (June 20), I have run a number of DHEAT2 parametric calculations for Surry. As we discussed, all calculations were run assuming any steam spike would develop too slowly to contribute to the DCH peak pressure. Recent CONTAIN calculations have also raised questions as to whether the steam from primary system blowdown could be added sufficiently rapidly to contribute effectively to the DCH peak pressure.

Hence, I also ran the two bounding cases with respect to the blowdown contribution, i.e., without the RCS steam and with 100%

of the steam from a fully pressurized RCS. Both series of calculations were run with the fraction of the corium participat-ing in DCH varying over the full range (0-100%)ium, with 100% metal reaction with oxygen assumed; initial cor temperature, composition, and mass as in CLWG SP-2; and an initial (pre-vessel-breach) containment pressure and temperature of 2.67 bars and 403 K, respectively. Results are as follows:

Without Blowdown Steam With Blowdown Steam Corium Fraction Final P Final T Final P Final T Participating (bars) (K) (bars) (K) 0.0 2.67 403. 3.69 404.

0.1 4.73 718. 5.77 634.

0.2 6.41 981. 7.56 834.

0.3 7.83 1207. 9.12 1011.

0.4 9.06 1407. 10.51 1171.

0.5 10.13 1583. 11.76 1317. ,

0.6 10.94 1722. 12.89 1451. '

O.7 11.79 1869. 13.90 1573. l 0.85 12.92 2069. 15.10 1722. J 1.00 13.88 2248. 16.33 1876. j It may be noted that the slope of the final-P vs. fraction-participating curve decreases significantly as the fraction participating increases. There are two reasons for this effect:

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.9 Dr. Lee June 23, 1986 (1) . As the temperature increases, the heat capacity of the containment atmosphere increases substantially, requiring a larger energy input to achieve the same delta-T and, hence, to achieve the same delta-P.

(2). As the final temperature increases, a greater fraction of the total energy still resides in the corium after thermal equilibration between the atmosphere and the corium is complete.

If the blowdown steam is added in time to participate effec-tively, the total heat capacity of the containment atmosphere is increased and, hence, both of the effects just noted are de-creased. For this reason, the difference between the with-blowdown and the no-blowdown results increases as the corium fraction participating increases. On the other hand, the rate of heat transfer from the gas to the structures will increase j rapidly as the temperature increases. Hence, as the corium participation fraction increases, it becomes increasingly

questionable as to whether the blowdown steam will be added i

sufficiently rapidly for its potential contribution to the peak pressures to be fully realized.

Finally, a word of caution about making detailed comparisons between these results and the results in the CLWG figure we have

, discussed in the past. The present calculations were performed 2 with a revised version of the DHEAT code which removes a number of simplifying approximations which time pressures had forced upon us in the CLWG work. These can make differences of at least

, a few tenths of a bar in the calculated results. The differences are expected to increase as the corium participation fraction increases; thus, they appear to be about 0.7 bar at 100% DCH

participation but less than 0.2 bar at 50% DCH.

I hope these results will be of some use to you. Please feel I

free to call upon me if I can be of further assistance (though I will be on vacation June 25-July 3).

Best regards, g & be W Y c David C. Williams Containment Modeling Division DCW:6449:mm

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